Method and apparatus for increasing power output and/or thermal efficiency of a gas turbine power plant

ABSTRACT

A gas turbine power plant having a modified gas turbine cycle (Brayton cycle) wherein the compressor inlet air is super-chilled before it enters the compressor. Superchilling, as defined herein, means to supercharge the inlet air to increase the pressure thereof to a pressure level moderately greater than the atmospheric pressure and to chill the supercharged air to decrease the temperature thereof, the preferred temperature level being in the vicinity of about 40* Fahrenheit. A heat recovery cycle is provided to supply the energy necessary to superchill the compressor inlet air.

United States Patent F oster-Pegg Mar. 12, 1974 [5 METHOD AND APPARATUSFOR 3,500,636 3/1970 Craig 60/39.]8 B X INCREASING POWER OUTPUT AND/ORFOREIGN PATENTS OR APPLICATIONS THERMAL EFFICIENCY OF A GAS URBINE POWERPLANT 505,044 8 1954 Canada 60/39.18 B T 679,007 9/1952 Great Britain60/3918 B [75] Inventor: Richard W. Foster-Pegg, Warren,

Primary Examiner-A1 Lawrence Smith [73] Assignee: Turbo-Development,Inc., New Assistant Exammer Mlchael K0020 York, Attorney, Agent, orF1rml(enyon and Kenyon Rellly Carr and Chapin [22] Filed: July 15, 1971[21] App]. No.: 162,911 57 ABSTRACT A gas turbine power plant having amodified gas tur- [52] US. Cl 60/39.02, 60/3918 B, 60/39.67 i Cycle(Brayton cycle) wherein the compressor [51] Int. Cl F02c 3/06, F020 7/10inlet air is supepchilled b f it enters the commas- [58] Fleld of Search60/39'18 R, 39-18 39-18 sor. Superchilling, as defined herein, means tosuper- 60/39-18 C1 39-67; 415/179 v charge the inlet air to increase thepressure thereof to a pressure level moderately greater than the atmo- 1I References Clted spheric pressure and to chill the supercharged air toUNITED STATES PATENTS decrease the temperature thereof, the preferredtem- 3,631,673 1/1972 Charrier 60/39.18 c Peratufe level being in hvicinity Of about Fahr- 2,663,144 12/1953 Nordstrom et a1. 1. 60/39.18 Benheit. A heat recovery cycle is provided to supply the 2,633,707 4/1953Hermitte etal. 60/39.18 B X energy necessary to superchill thecompressor inlet 2,322,717 6/1943 air. 3,479,541 11/1969 3,153,44210/1964 Silvern 62/467 UX 6 Claims, 9 Drawing Figures Vase/Var 30/454Facade/mu: f/ex r cvmesssoe PATENTEB m 12 m4 SHEET 8 OF 8 KEQQ W lk 8v?EMA/86$ V Army/yam PATENTEBm 12 1914 SHEEI 7 OF 8 wav 4 P/vas PATENTEI]IIAR 1 2 I974 sum 3 or 8"" METHOD AND APPARATUS FOR INCREASING POWEROUTPUT AND/OR THERMAL EFFICIENCY OF A GAS TURBINE POWER PLANT BACKGROUNDOF THE INVENTION The present invention broadly relates to a modified gasturbine cycle for a gas turbine power plant. More particularly, theinvention relates to a modified gas turbine cycle wherein the compressorinlet air is superchilled to increase the power output and/or thethermal efficiency of the gas turbine power plant.

Gas turbine power plants have been used for many years to generateelectrical power, particularly during periods when demand for electricalpower is greatest. The peak demand periods generally occur during thehottest weather when the ambient temperature of the air is high. Thehigh temperature of the compressor inlet air at these timessignificantly reduces the performance of a gas turbine power plant bydecreasing the power output and/or thermal efficiency of the turbine.Consequently, during periods of more moderate or normal ambient airtemperatures, the power required of the stationary gas turbine may besubstantiallybelow that which the turbine is capable of producing atthese conditions so that adequate capacity is available when theambient'temperature of the air is high.

Electrical utilities and gas turbine manufacturers have considerableincentives to increase the power output and/or thermal efficiency ofstationary gas turbine power plants, and much effort has been expendedto reap the rewards occasioned by each increase therein. Thus,stationary gas turbine power plants occasionally include various meansfor modifying the basic gas turbine cycle such as intercoolers,regenerators and recuperators which increase the power output and/orthermal efficiency of the gas turbine power plant. In. addition, limiteduse has been made of supercharging the compressor inlet air and coolingthe supercharged air to increase the power output of the gas turbinepower plant. However, at the present time such uses extend only tosupercharging with electric motor driven fans and to cooling withevaporative coolers. For example, see Foster-Pegg, R.W., superchargingof Gas Turbines by Forced Draft Fans with Evaporative Intercooling,"American Society of Mechanical Engineers, Paper No. 65-GTP 8 (1965).Thus, the prior art does not disclose supercharging compressor inlet airwith waste heat energy from the gas turbine exhaust gases. Further,chilling the compressor inlet air to low tem peratures is also known.For example, see US. Pat. No. 2,322,717 for Apparatus For CombustionTurbines issued June 22, 1943. However, chilling of the compressor inletair has not been adopted by electrical utilities and gas turbinemanufacturers, except when a means for chilling the intake air isalready available or is being installed for another purpose.

At present, no gas turbine power plant has been installed with achilling means provided for the primary purpose of chilling thecompressor inlet-air. Thus, the prior art does not disclose chilling thecompressor inlet air with a refrigeration system having a compressordriven by waste-heat energy from the exhaust gases of the gas turbine.Further, the prior art does not include supercharging and chilling thecompressor inlet air.

Despite the incentives to increase the power output and/or thermalefficiency of gas turbine power plants and the efforts that have beenexpended in this regard, present gas turbine power plants generallyremain uneconomical for continuous base load electrical power generationwhen compared to steam turbine power plants or combined steam and gasturbine power plants.

SUMMARY OF THE INVENTION A gas turbine power plant is provided having abasic 7 gas turbine cycle comprising the following steps: compressingthe inlet air from the atmosphere in a compressor; heating thecompressed air in a combustor; and expanding the heated, compressed airthrough a turbine.

According to one embodiment of the present invention, the power outputand/or the thermal efficiency of the basic gas turbine cycle describedabove are significantly improved by the additional step of Superchillingthe ambient inlet air before it enters the compressor of the gas turbinepower plant. Superchilling, as used herein, means supercharging theinlet air to the compressor of the gas turbine to increase the pressurethereof to a pressure level moderately greater than the atmosphericpressure by means of a low pressure ratio device and chilling thesupercharged inlet air to reduce the temperature thereof to atemperature at least as low as the temperature that could be obtainedwith an evaporative cooler cooling the supercharged air under ambientconditions then present. Chilling is accomplished by the direct transferof heat from the supercharged inlet air to the refrigerant of arefrigeration system.

The term refrigerant is used herein in a broad and not a restrictionsenseof the word. The term refrigerant includes all fluids (such asliquids, vapors, and gas) to which heat from the inlet air can betransferred to chill the air. Thus, the term refrigerant is not limitedto those liquids which produce refrigeration by their evaporation from aliquid to a gaseous under reduced pressure. By way of example, the termrefrigerant can include liquid, such as a brine, which serves as anintermediate refrigerant between a primary refrigerant used to cool thefluid and the inlet air which is chilled by the direct transfer of heatto the fluid. F urther, the term refrigerant" includes ice which may beused to chill the inlet air directly or to cool an intermediaterefrigerant such as a brine.

The compressor inlet air is preferably supercharged to increase thepressure thereof in accordance with a supercharging pressure ratio inthe range of pressure ratios extending from about 1.1 to about 1.75. Onepreferred low pressure ratio device for increasing the pressure of thecompressor inlet air is a fan device, for example, a conventional singlestage, dual flow centrifugal blower. Supercharging pressure ratios abovethose obtainable with a single stage fan device can be obtained by twostages of supercharging with such a fan device.

Generally speaking, since ambient air usually contains some moisture,the lower temperature limit for the chilling of the supercharged gas isa temperature in the vicinity of the temperature at which concomitantchilling of the moisture in the inlet air could form ice accumulationson heat transfer surfaces used to chill the inlet air. To avoid iceaccumulations, the temperature of a heat transfer surface used to chillthe inlet air should be maintained at a temperature at least as high asthe freezing temperature of the moisture in the inlet air. Thus, as thechilling temperature level of the inlet air approaches the freezingtemperature of the moisture in the inlet air, an extensive heat transfersurface is required to chill the air. Accordingly, a chillingtemperature level in the vicinity of the range of temperatures extendingfrom about 35 degrees Fahrenheit to about 40 Fahrenheit is preferred.

However, lower chilling temperatures are possible. For example, a meansfor removing the ice formed on the heat transfer surfaces can beprovided thus enabling the compressor inlet air to be chilled to atemperature significantly below the preferred range of temperatures.Further, if a significant degree of moisture is not present in thecompressor inlet air, the chilling temperature can also extendconsiderablybelow the preferred range of temperatures.

The energy required to chill the inlet air is increased by moisturecontained in the air. Since the supercharged inlet air is generallychilled to a temperature below the dew point of the inlet air, moisturein the inlet air in excess of the saturated moisture content of the airat the chilling temperature will be condensed in the chilling means.Accordingly, under humid conditions, the total cooling requirement forthe chilling means significantly exceeds the sensible heat cooling thatwould be required for dry air alone.

The compressor inlet air can be chilled both before and after the inletair has been supercharged, or the inlet air can be chilled only after ithas been supercharged. Although chilling both before and aftersupercharging can result in increased capital expenditures, it can beadvantageous under certain circumstances. Initial chilling of the inletair reduces the power required to supercharge a given inlet air massflow rate, and thus reduces the total power required to chill the inletair before it enters the compressor since the heat input to the inletair caused by supercharging is reduced. The reduction of power tosupercharge the inlet air results from the lower temperature of the airentering the supercharging means and from the decreased mass flow ratethrough the supercharging means caused by the moisture condensed fromthe inlet air during the initial chilling thereof. Further, the reducedpower required to charge the inlet air to a given pressure permits ahigher supercharge pressure to be obtained when a heat recovery cycle,to be discussed hereinafter, is provided to drive the superchargingmeans and the chilling means.

According to another embodiment of the present invention, a heatrecovery cycle is provided to supply the energy necessary to superchillthe compressor inlet air. For example, a waste-heat boiler can beprovided to generate steam by utilizing the waste-heat in the turbineexhaust gases. The steam is subsequently expanded through a first and asecond steam turbine. The output shaft of the first steam turbine iscoupled to drive the low pressure ratio device for supercharging thecompressor inlet air. The output shaft of the second steam turbine iscoupled to drive a compression refrigeration unit for chilling thecompressor inlet air.

As will be more fully illustrated below, significant and heretoforeunforeseen benefits result from superchilling the compressor inlet air.Superchilling the compressor inlet air significantly increases the airmass flow rate to the compressor of the gas turbine power plant at afixed volume flow rate by increasing the pressure and decreasing thetemperature of the inlet air. Superchilling also increases the gasturbine inlet pressure thereby increasing the expansion ratio across thegas turbine. The increased air mass flow rate through the gas turbinepower plant and the increased expansion ratio across the turbine providea significant increase in the poweroutput of the gas turbine powerplant. F urther, the lower compressor inlet air temperature permits thegas turbine power plant to be operated at near optimum power outputirrespective of the ambient air temperature. When the heat recoverycycleis provided to superchill the compressor inlet air, an additionalsignificant increase in the power, output results as well as animprovement in the thermal efficiency of the gas turbine.

Accordingly, it is an objective of the present invention to provide agas turbine power plant having increased power output and/or thermalefficiency.

Another object is to increase the power output and- /or the thermalefficiency of the gas r turbine power plant when the ambient temperatureof the air is high.

Still another object is to provide a gas turbine power plant whereinambient inlet air is superchilled before it enters the compressor of thegas turbine for increasing the power output and/or the thermalefficiency of the turbine cycle.

A further object is to provide a gas turbine power plant whereinwaste-heat in the turbine exhaust gases is utilized to supply the energyfor superchilling the compressor inlet air.

A still further object is to provide a gas turbine power plant fordriving an electric generator wherein the compressor inlet air issuperchilled before it enters the compressor, and the electric generatorcooling medium is chilled for simultaneously increasing the power outputand/or the thermal efficiency of the gas turbine and the generatingcapacity of the electric generator.

A still further object is to provide a gas turbine power plant whereinthe waste-heat in the turbine exhaust gases is utilized to supply theenergy for superchilling the compressor inlet air and for chilling theelectric generator cooling medium.

These and other objects and advantages of the gas turbine power plant ofthe present invention will become more apparent from the followingdescription, when read in conjunction with the accompanying drawings,wherein corresponding parts of each figure have corresponding numbers.

FIG. '1 is a schematic diagram of one embodiment of the presentinvention wherein the compressor inlet air is supercharged andsubsequently chilled before the air enters the compression stage of thegas turbine.

FIG. 2 is a schematic diagram of another embodiment of the presentinvention wherein the supercharger and chiller are driven by waste-heatenergy recovered from the turbine exhaust gases.

FIG. 3 is a schematic diagram of still another embodiment of the presentinvention showing selected operating characteristics for a complete gasturbine cycle adjacent the individual components.

FIG. 4 is a graph showing the power output of the embodiment of the gasturbine power plant illustrated in FIG. 3 as a function of the degree ofsuperchilling of the compressor inlet air.

FIG. 5 is a graph showing the heat rate of the embodiment of the gasturbine power plant illustrated in FIG. 3 as a function of the degree ofsuperchilling of the compressor inlet air.

FIG. 6 is a schematic diagram of the embodiment of the gas turbine powerplant of FIG. 2 showing selected operating characteristics for acomplete gas turbine cycle adjacent the individual components.

FIG. 7 is a schematic diagram of still another embodiment of the presentinvention wherein the compressor inlet air is chilled before and afterit is supercharged.

FIG. 8 is a schematic diagram of the embodiment of the gas turbine powerplant illustrated in FIG. 2 showing a second set of selected operatingcharacteristics for a complete gas turbine cycle adjacent the individualcomponents.

FIG. 9 is a schematic diagram of still another embodiment of the presentinvention showing selected operating characteristics for a complete gasturbine cycle adjacent the individual components.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, onepreferred embodiment of the improved gas turbine power plant isschematically illustrated in FIG. 1. The improvement of the presentinvention is schematically shown in conjunction with-a conventionalopen-cycle, single shaft gas turbine power plant. The gas turbine powerplant comprises a compressor 10 for compressing the inlet air from theatmosphere, a combustor 11 for heating the compressed air, and a turbine12 for expanding the heated, compressed air. The turbine 12 is operablycoupled to drive the compressor 10 and an electric generator 13 by meansof shaft 14.

According to the present invention, the power output and/or the thermalefficiency of the gas turbine described above are significantlyincreased by superchilling the inlet air before it enters the compressorof the gas turbine.

Thus, referring to FIG. 1, a supercharging means 15 is provided whichcomprises a low pressure ratio device, conveniently shown as a fan 16,driven by an electric motor 17. Inlet air is drawn through the fan 16thereby increasing the pressure thereof to a pressure level moderatelygreater than the atmospheric pressure. Once the inlet air has beensupercharged, it is ducted to a chilling means 18.

The chilling means 18 is conveniently shown as a compressionrefrigeration unit 19 which comprises an evaporator coil 20 in which aliquid refrigerant boils at a low temperature, a compressor 21 driven byan electric motor 22 for raising the pressure and temperature of thegaseous refrigerant from the evaporator coil 20, a condenser 23 in whichthe refrigerant from the compressor 21 discharges heat to a secondarycooling medium such as water, and an expansion valve 24 for expandingthe liquid refrigerant from the high pressure level in the condenser 21to the low pressure level in the evaporator coil 20. The superchargedinlet air is ducted across the evaporator coil 20 where the air ischilled as heat from the air is transferred to the expanded gaseousrefrigerant therein.

The secondary cooling medium is circulated through the coil 25 of thecondenser 23 by a circulating pump 26 where the gaseous refrigerantcondenses to a liquid and releases heat to the cooling medium. Thecooling medium subsequently circulates through a cooling coil 27 of acooling tower 28 where the cooling medium discharges heat to aircirculated across the cooling coil 27 by a cooling fan 29, driven by anelectric motor 30.

To illustrate the increased performance of a gas turbine power plantobtained by superchilling the compressor inlet air, the power output andthermal efficiency of various embodiments of the gas turbine power plantare described below. The ideal gas turbine power plant assumed for someof the comparisonsis a 25 megawatt gas turbine power plant having anideal gas turbine cycle (Brayton Cycle) rated at a compressor inlettemperature of about F. and a compressor inlet pressure of about 392inches of water which corresponds to the pressure at about a 1,000 footelevation. The ideal cycle has no inlet or exhaust pressure losses.Assuming a compressorinlet mass flow rate of about 1 X 10 pounds of airper hour, a combustor fuel requirement of about 300 X 10 Btu/Hr LI-IV(Lower Heating Value), and a gas turbine exhaust temperature andpressure of about 895F. and about 392 inches of water, respectively, theideal gas turbine power plant would produce about 25 megawatts (ratedpower output) at a heat rate of about 12,000 Btu/Kwh LI-IV.

The performance of the ideal 25 megawatt gas turbine power plant issignificantly reduced when the gas turbine is operated under warmweather conditions. If the ideal gas turbine were operated at highambient inlet air temperatures of about F. dry bulb and 80F. wet bulb atabout a 1,000 foot elevation with an inlet pressure loss of about 2inches of water and an exhaust pressure loss of about 4 inches of water,the ideal gas turbine would produce about 87.5 per cent of the ratedpower output (21.6 megawatts) at a heat rate of about 13,000 Btu/KwhLI-IV. The power output and heat rate calculations are based upon acompressor mass flow rate of about 0.954 X 10 pounds of air per hour, acombustor fuel requirement of about 281.7 X 10 Btu/hr Ll-IV, and aturbine exhaust pressure of about 396 inches of water. The ideal 25megawatt gas turbine having the above assumed inlet and exhaust pressurelosses will hereinafter be referred to as the standard gas turbine.

Superchilling the compressor inlet air of the standard gas turbinedescribed above, as shown in FIG. 1, significantly increases the poweroutput and/or thermal efficiency of the gas turbine. For example, assumethe following operating conditions: inlet air temperatures, pressure andmass flow rates of about 100F. dry bulb,

about 80F. wet bulb, about 390 inches of water, about 1.223 X 10 poundsof air per hour and about 21.4 x 10 pounds of water per hour; acombustor fuel requirement of about 382.3 X 10 Btu/hr LI-IV; and aturbine exhaust temperature of about 823F. Supercharg ing the compressorinlet air of the standard gas turbine to moderately raise the pressurethereof from about 390 inches of water to about 448 inches of water witha motor driven fan 16, and chilling the supercharged compressor inletair to about 40F. with a motor driven compression refrigeration unit 19increases the net power output of the standard gas turbine to about 125per cent of rated power output (31.17 megawatts) at a heat rate of about12,300 Btu/Kwh Ll-IV. The motor driven fan 16 would require about 2,750kilowatts to supercharge the inlet air. The refrigeration unit 19 wouldrequire about 3,892 kilowatts to chill the supercharged air. Thus, ofthe about 37.8 megawatts of electrical power generated by the standardgas turbine, about 6,642 kilowatts are consumed by the superchillingthereby providing a net power output of about 31.17 megawatts.

Another preferred embodiment of' the present invention is schematicallyillustrated in FIG. 2. As described above, the supercharging means 15and the chilling means 18 of the present invention are shown inconjunction with a conventional open cycle, single shaft gas turbinepower plant. However, in FIG. 2, the compressedair from the compressoris heated in a regenerator'by waste heat in the turbine exhaust gases.Thus, the compressed air is ducted through the coil 35 of a regenerativeheat exchanger 36 before it enters the combustor 11. Most of the turbineexhaust gas is ducted across the heat exchanger coil 35 for heating thecompressed air passing therethrough.

According to the present invention, the power output and/or thermalefficiency of the gas turbine power plant are still more significantlyincreased by the addition of a heat recovery cycle wherein residualwasteheat in the turbine exhaust gases is recovered and converted intomechanical energy for driving the supercharging means and the chillingmeans 18. Thus, referring to FIG. 2, a closed steam cycle is providedwherein a waste-heat boiler 37 generates steam from the residualwaste-heat in the turbine exhaust gases. The steam generated thereby isexpanded through a first steam turbine 38, operably coupled to drive thesupercharging means 15, and a second steam turbine 39, operably coupledto drive the chilling means 18.

The turbine exhaust gases from the regenerative heat exchanger 36 areducted through the waste-heat boiler 37. The residual waste-heat in theexhaust gas generates steam from water pumped through the coils 40- ofthe waste-heat boiler 37. The steam generated thereby is subsequentlycirculated through the coil 41 of a steam heat exchanger 42 where thewaste-heat in the remainder of the turbine exhaust gases superheats thesteam. The remainder of the exhaust gases is then ducted through thewaste-heat boiler 37 to supplement the waste-heating by the turbineexhaust gases from the regenerative heater 36.

A portion of the superheated steam generated by the waste-heat boiler isexpanded in'the first steam turbine 38 which is operably coupled todrive the fan 16 of the supercharging means 15. The remainder of thesuperheated steam is expanded in the second steam turbine 39 which isoperably coupled to drive the compressor 21 of the compression cyclerefrigeration unit 19. The steam discharged from the steam turbines 38and 39 is condensed in condensors 43 and 44 and is recycled to thewaste-heat boiler 37 by return pumps 45 and 46. The cooling medium forthe condensers 43 and 44 is conveniently provided from the secondarycooling medium for the condenser coil 23. Thus, the circulating pumpalso circulates the cooling medium from the cooling coil 26 through thecondenser coil 23 of the refrigeration unit 19 and through the coils 47and 48 of the condensers 43 and 44.

The performance of the gas turbine power plant is still further improvedwhen the electric generating capacity of the electric generator isincreased to complement the increased shaft output of the gas turbinepower plant. An electric generator cooling means 50 is provided to chillthe generator cooling medium. The cooling means 50 comprises a generatorcooling coil 51 disposed within the electric generator 13 in aheattransfer relationship withthe generator cooling circuit 52. Theliquid refrigerant from the chilling means 18 is circulates through thecoil 51 to substantially chill the generator cooling medium flowing inthe circuit 52. As illustrated in FIG. 3, the generator cooling coil 51and the evaporator coil 20 are connected in parallel between theexpansion valve 24 and the compressor 21.

The liquid refrigerant expands through the expansion valve 24 and iscirculated through the generator cooling coil 51 where the refrigerantboils to chill the generator cooling medium.

As noted above, superchilling the compressor inlet air according to thepresent invention significantly increases the power output and/orthermal efficiency of a gas turbine power plant. For example, anotherembodiment of the present invention is illustrated in FIG. 3. Theembodiment of the gas turbine power plant of FIG. 3 is similar to thegas turbine power plant illustrated in FIG. 2, however, the compressedair from the compressor 10 is not regeneratively heated by aregenerative heat exchanger 36.

The operating characteristics of the gas turbine power plant listed inFIG. 3 are calculated on the'basis of a compressor inlet pressure lossof about 2 inches of water and a turbine exhaust pressure loss of about4 inches of water. An additional inlet pressure loss of about 2 inchesof water is assumed for the chilling means 19 and an additional exhaustpressure loss of about 4 inches of water is assumed for the waste heatboiler 37. Thus, the gas turbine of FIG. 3 having the compressor inletair supercharged to increase the compressor inlet pressure by about 58inches of water and chilled to reduce the temperature of the compressorinlet air to about 40F. would produce about 15 l per cent of the ratedpower output (37.8 megawatts) at a heat rate of about 10,130 Btu/KwhLHV.

Now, referring to FIGS. 4 and 5, the performance of the standard gasturbine power plant described above is compared with the performance ofthe gas turbine power plant of FIG. 3 under varying levels'ofsupercharging and chilling. The performances are compared for highambient inlet air temperatures of about 100F. dry bulb and about F. webbulb at about a 1,000 foot elevation. An inlet pressure loss of about 2inches of water and an exhaust pressure loss of about 4 inches of waterare assumed for the standard gas turbine power plant. An additionalinlet pressure loss of about 2 inches of water is assumed for thechilling means and an additional exhaust pressure loss of about 4inches'of water is assumed for the heat recoverycycle.

The performance of the standard gas turbine power plant is representedin FIGS. 3 and 4 by the points marked A on the F. line (no chilling)corresponding to zero pressure increase (no supercharging). As

indicated therein, the standard gas turbine power plant would produceabout 87.5 per cent of the rated powerv output (21.6 megawatts) at aheat rate of about 13,000 Btu/Kwh LI-IV. In comparison, the performanceof the gas turbine power plant of FIG. 3 is indicated by the I pointsmarked 8.

The increase in power output and/or thermal efficiency of a gas turbinepower plant having superchilled compressor inlet air is still moresignificant when the gas turbine cycle includes regenerative heating ofthe compressor outlet air, as shown in FIG. 6.'The embodiment of thepresent invention illustrated in FIG. 6 is the same as the embodimentillustrated in FIG. 2. Referring to FIG. 6, selected characteristics ofthe gas turbine power plant for one set of operating conditions arelisted adjacent the individual components thereof. The same ambientconditions and pressure losses assumed for the calculations presented inFIGS. 4 and 5 were applied to the calculations for FIG. 6. The poweroutput for the superchilled gas turbine powerplant of FIG. 6 is about39.6 megawatts at a heat rate about 8,480 Btu/Kwh LHV.

By way of comparison, the power output of a conventional regenerativegas turbine power plant would be about 26.1 megawatts at a heat rate ofabout 9,850 Btu/Kwh Ll-IV. These calculations are based upon thefollowing conditions: air temperature, pressure and mass flow rates ofabout 80F., about 388 inches of water, and about 0.96 X 10 pounds of airper hour and about 13.3 X 10 pounds of water per hour, respectively; acompressor compression ratio of about.9.0 and a turbine expansion ratioof about 7.8; a compressor outlet temperature of about 543F., acombustor inlet temperature of about 839F. and a turbine inlet temperature of about 1750F.p a combustor fuel requirement of about 257.3 X 10Btu/Hr LHL; gas turbine exhaust temperature and pressure of about963F.'and about 404 inches of water, respectively; and regeneratorexhaust temperature and pressure of about 743F. and about 396 inches ofwater, respectively.

As indicated above, the compressor inlet air can also be chilled bothbefore and-after the air is supercharged. An embodiment of the gasturbine power plant having such dual chilling is illustrated in FIG. 7.The chilling means 18 comprises a compression refrigeration unit 19, asdescribed above with respect to FIG. 1, but having a first evaporatorcoil 20a and a second evaporator coil 20b. The inlet air is initiallydrawn across the first evaporator coil 20a where the air is chilled asheat from the air is transferred to the coil. The inlet air is nextdrawn through the fan 16 where the air is supercharged. The superchargedinlet air which has been heated by the work applied to the airby the fan16 is again chilled as it is ducted across the second evaporator coil20b before it enters the compressor 10.

Selected characteristics for the gas turbine power plant'for one set ofoperating conditions are listed in FIG. 7. The power output for the gasturbine is about 42.8 megawatts at a heat rate of about 9,180 Btu/KwhLl-IV.

A further example of the significant increase in thermal efficiencyand/or power output obtained through superchilling is illustrated inFIG. 8. The embodiment of the gas turbine power plant illustratedtherein is similar to the embodiment of FIG. 2; however, the individualcomponents are considerably larger to accommodate the increased air massflow rate necessary to generate sufficient power to drive the largergenerator 13. Although the same pressure losses are assumed for thecalculations listed in FIG. 8, it will be noted that the assumed ambientair temperatures are lower than the ambient air temperatures assumedabove. At these conditions, the superchilled gas turbine power plantwould produce about 77.0 megawatts of power at a heat rate of about7,060 Btu/Kwh LI-IV.

The heat rate of the superchilled gas turbine power plant of FIG. 8 isremarkably low for a gas turbine power plant and it is highlycompetitive with the heat rates obtained with steam turbine powerplants.

Superchilling the compressor inlet air with energy provided by a heatrecovery cycle and regeneratively heating the compressed air before itenters the combustor can utilize substantially all of the waste-heat inthe turbine exhaust gases. As a practical matter, maximum regeneratorefficiency would commonly be on the order of about seventy-five per centso that some waste-heat would always be available for the heat recoverycycle. The waste-heat boiler can include an economizer and/or acombination low pressure boiler and deaerator.

Maximum efficiency of superchilling will generally occur at maximumregenerator efficiency with as much of the residual waste-heat leavingthe re generator being utilized for the heat recovery cycle. The abilityof superchilling to operate at maximum efficiency can be coupled withhigh power capability by selectively increasing the energy input to therecuperative cycle thereby increasing the degree of superchilling. Thus,referring to FIG. 9, still another embodiment of the present inventionis illustrated wherein a regenerator bypass circuit 49 is provided toduct the turbine exhaust gases around the regenerator 36 and directlyinto the waste-heat boiler 37 of the heat recovery cycle therebyincreasing the energy available for superchilling the inlet air. Anadjustable bypassvalve 50 in the circuit 49 permits the power outputand/or thermal efficiency of the gas turbine power plant to be modulatedin a controlled manner.

Power output of the gas turbine power plant below the point of maximumefficiency can also be effectively modulated. Preferably, thismodulation would be accomplished by reducing the degree ofsupercharging, for example, throttling the first steam turbine 38coupled to drive the fan 16, while maintaining the same degree ofchilling. Still lower power outputs could be obtained by controlledexhausting to the atmosphere of the turbine exhaust gases from theregenerator 36 to reduce the energy input to the heat recovery cyclethus reducing the degree of chilling. With complete exhausting of theturbine exhaust gases, the gas turbine power plant operates in theconventional manner without any supercharging or chilling of thecompressor inlet air.

Accordingly, referring again to FIG. 9, a second adjustable bypass valve51 is provided to permit selective venting to the atmosphere of theturbine exhaust gases from the regenerative heat exchanger 36 and/or thebypass circuit 49. Adjustment of the second bypass valve 51 providesselective reduction of the energy available to the heat recovery cyclewhich in turn reduces the degree of superchilling of the compressorinlet air.

By way of further example, the operating characteristics for theembodiment of the gas turbine power plant of FIG. 9 are listed therein.The superchilled gas turbine power plant would produce about 39.6megawatts of power at a heat rate of about 8480 Btu/Kwh LI-IV.

Other means are available to supercharge the ambient-inlet air. Forexample, fan 16 can be replaced by a moderately low pressure risecompressor or blower. Similarly, other means are also available to chillthe inlet air. For example, the compression refrigeration unit 19 can bereplaced by an absorption refrigeration unit. Generally speaking, in anabsorption refrigeration unit, the compressor 21 and motor 22 in thecompression refrigeration unit would be replaced by an absorber, agenerator, a pump, a heat exchanger and a reducing valve. Waste-heat inthe turbine exhaust gases would provide the heat input to the absorptionrefrigeration unit.

Although the gas turbine power plant of the present invention has beendescribedas a power source for an electrical generator, it is to beunderstood that the improved gas turbine power plant has otherapplications. For example, the gas turbine power plant has applicationas a natural gas pipeline compressor drive.

The embodiments of the gas turbine power plant described above are forthe purpose, of illustrating the broader aspects of the presentinvention, and the advantages attendant therein. Other modifications andvariations of the embodiments will-be apparent to those skilled in mean,and they may be made without de- 1. An improved gas turbine havingincreased performance, the gas turbine including a compressor forreceiving inlet gas and compressing the same, means for heating thecompressed gas, and a turbine for expanding the heated compressed gas,the improvement comprising;

a. means for supercharging the inlet gas before it is received by thecompressor; and

b. means for chilling the supercharged inlet gas before it is receivedby the compressor, the chilling means including a refrigerant for thedirect transfer of heat from the supercharged gas thereto; and e 0.means for regeneratively heating the compressed gas from the compressorwith waste-heat from the exhaust gases of the turbine before thecompressed gas passes to the compressed gas heating means; and v (1.means for recovering a portion of.the waste-heat energy from the exhaustgases of the turbine and for converting the waste-heat energy intoenergy for driving the supercharging means and for driving the chillingmeans; and v e. means for selectively controlling the portion of thewaste-heat energy converted to energy for driving the superchargingmeans and for driving the chilling means for providing selective controlover the amount of energy available to superchill the inlet gas therebyproviding for selective control of the performance of the gas turbine.

2. An improved gas turbine having increased performance, the gas turbineincluding a compressor for receiving inlet gas and compressing the same,means for heating the compressed gas, and a turbine for expanding theheated compressed gas, the improvement comprising:

a. means for supercharging the inlet gas before it is received by thecompressor; and

b. means for chilling the supercharged inlet gas before it is receivedby the compressor, the chilling means including a refrigerant for thedirect transfer of heat from the supercharged gas thereto; and

c. means for recovering a portion of the wasteheat energy from theexhaust gases of the turbine and for converting the waste-heat energyinto energy for driving the supercharging means and for driving thechilling means; and

d. means for selectively controlling the portion of the waste-heatenergy converted to energy for driving the supercharging means and fordriving the chill ing means for providing selective control over theamount of energy available to superchill the inlet gas thereby providingfor selective control of the performance of the gas turbine.

3. An improved gas turbine having increased performance, the gas'turbineincluding a compressor for receiving inlet gas and compressing the same,means for heating the compressed gas, and a turbine for expanding theheated compressed gas, the improvement comprising: v v

a. means for supercharging the inlet gas before it is received by thecompressor; and

b. means for chilling the supercharged inlet gas before it is receivedby the compressor; and

c. means for recovering a portion of the wasteheat energy from theexhaust gases of the turbine and for converting the waste-heat energyinto energy for driving the supercharging means and for driving thechilling means;

d. means for selectively controlling the portion of the waste-heatenergy converted to energy for-driving the supercharging means and fordriving the chilling means for providing selective control over theamount of energy available to superchill the inlet gas thereby providingfor selective control of the performance of the gas turbine.

, 4. An improved gas turbine according to claim 3, further comprisingmeans 'for regneratively heating the compressed gas from the compressorwith waste-heat from the exhaust gases of the turbine before thecompressed gas passes to the compressed gas heating means.

5. A method for increasing the performance of a gas turbine, the gas-turbine including a compressor for receiving inlet gas andcompressing-the same, means for heating the compressed gas, and aturbine for expanding the heated compressed gas to extract worktherefrom, the method comprising the steps of:

a. supercharging the inlet gas by a fan or a blower device before it isreceived by the compressor by increasing the pressure of the inlet gasin accordance with a supercharging pressure ratio in a range of pressureratios extending from about 1.1 to about 1.75; i

b. chilling the supercharged inlet gas before it is received bythe-compressor by the direct transfer of heat from the supercharged gasto the refrigerant of a refrigeration system;

c. regeneratively heating the compressed gas from the compressor withwaste-heat from the exhaust gases of the turbine;

d. recovering a portion of the waste-heat energy from the exhaust gasesof the turbine and converting the waste-heat energy into energy forsuperchilling the compressor inlet air; and I e. selectively controllingthe portion of the wasteheat energy converted to energy forsuperchilling the compressor inlet air thereby selectively controllingthe performance of the gas turbine.

before it is received by the compressor by increasing the pressure ofthe inlet gas in accordance with a supercharging pressure ratio in arange of pressure ratios extending from about 1.1 to about 1.75;

b. means for chilling the supercharged inlet gas before it is receivedby the compressor, the chilling means including a refrigerant for thedirect transfer of heat from the supercharged gas thereto;

c. means for regeneratively heating the compressed gas from thecompressor with waste-heat from the exhaust gases of the turbine beforethe compressed gas passes to the compressed gas heating means;

d. means for recovering a portion of the waste-heat energy from theexhaust gases of the turbine and for converting the waste-heat energyinto energy for driving the supercharging means and for driving thechilling means; and

. means for selectively controlling the portion of the waste-heat energyconverted to energy for driving the supercharging means and for drivingthe chilling means for providing selective control over the amount ofenergy available to superchill the inlet gas thereby providing forselective control of the performance of the gas turbine.

1. An improved gas turbine having increased performance, the gas turbineincluding a compressor for receiving inlet gas and compressing the same,means for heating the compressed gas, and a turbine for expanding theheated compressed gas, the improvement comprising; a. means forsupercharging the inlet gas before it is received by the compressor; andb. means for chilling the supercharged inlet gas before it is receivedby the compressor, the chilling means including a refrigerant for thedirect transfer of heat from the supercharged gas thereto; and c. meansfor regeneratively heating the compressed gas from the compressor withwaste-heat from the exhaust gases of the turbine before the compressedgas passes to the compressed gas heating means; and d. means forrecovering a portion of the waste-heat energy from the exhaust gases ofthe turbine and for converting the wasteheat energy into energy fordriving the supercharging means and for driving the chilling means; ande. means for selectively controlling the portion of the wasteheat energyconverted to energy for driving the supercharging means and for drivingthe chilling means for providing selective control over the amount ofenergy available to superchill the inlet gas thereby providing forselective control of the performance of the gas turbine.
 2. An improvedgas turbine having increased performance, the gas turbine including acompressor for receiving inlet gas and compressing the same, means forheating the compressed gas, and a turbine for expanding the heatedcompressed gas, the improvement comprising: a. means for superchargingthe inlet gas before it is received by the compressor; and b. means forchilling the supercharged inlet gas before it is received by thecompressor, the chilling means including a refrigerant for the directtransfer of heat from the supercharged gas thereto; and c. means forrecovering a portion of the wasteheat energy from the exhaust gases ofthe turbine and for converting the waste-heat energy intO energy fordriving the supercharging means and for driving the chilling means; andd. means for selectively controlling the portion of the waste-heatenergy converted to energy for driving the supercharging means and fordriving the chilling means for providing selective control over theamount of energy available to superchill the inlet gas thereby providingfor selective control of the performance of the gas turbine.
 3. Animproved gas turbine having increased performance, the gas turbineincluding a compressor for receiving inlet gas and compressing the same,means for heating the compressed gas, and a turbine for expanding theheated compressed gas, the improvement comprising: a. means forsupercharging the inlet gas before it is received by the compressor; andb. means for chilling the supercharged inlet gas before it is receivedby the compressor; and c. means for recovering a portion of thewaste-heat energy from the exhaust gases of the turbine and forconverting the waste-heat energy into energy for driving thesupercharging means and for driving the chilling means; d. means forselectively controlling the portion of the waste-heat energy convertedto energy for driving the supercharging means and for driving thechilling means for providing selective control over the amount of energyavailable to superchill the inlet gas thereby providing for selectivecontrol of the performance of the gas turbine.
 4. An improved gasturbine according to claim 3, further comprising means for regnerativelyheating the compressed gas from the compressor with waste-heat from theexhaust gases of the turbine before the compressed gas passes to thecompressed gas heating means.
 5. A method for increasing the performanceof a gas turbine, the gas turbine including a compressor for receivinginlet gas and compressing the same, means for heating the compressedgas, and a turbine for expanding the heated compressed gas to extractwork therefrom, the method comprising the steps of: a. supercharging theinlet gas by a fan or a blower device before it is received by thecompressor by increasing the pressure of the inlet gas in accordancewith a supercharging pressure ratio in a range of pressure ratiosextending from about 1.1 to about 1.75; b. chilling the superchargedinlet gas before it is received by the compressor by the direct transferof heat from the supercharged gas to the refrigerant of a refrigerationsystem; c. regeneratively heating the compressed gas from the compressorwith waste-heat from the exhaust gases of the turbine; d. recovering aportion of the waste-heat energy from the exhaust gases of the turbineand converting the waste-heat energy into energy for superchilling thecompressor inlet air; and e. selectively controlling the portion of thewaste-heat energy converted to energy for superchilling the compressorinlet air thereby selectively controlling the performance of the gasturbine.
 6. An improved gas turbine having increased performance, thegas turbine including a compressor for receiving inlet gas andcompressing the same, means for heating the compressed gas, and aturbine for expanding the heated compressed gas, the improvementcomprising: a. fan or blower means for supercharging the inlet gasbefore it is received by the compressor by increasing the pressure ofthe inlet gas in accordance with a supercharging pressure ratio in arange of pressure ratios extending from about 1.1 to about 1.75; b.means for chilling the supercharged inlet gas before it is received bythe compressor, the chilling means including a refrigerant for thedirect transfer of heat from the supercharged gas thereto; c. means forregeneratively heating the compressed gas from the compressor withwaste-heat from the exhaust gases of the turbine before the compressedgas passes to the compressed gas heating means; d. means for recoveringa portion of the waste-heat energy from the exhAust gases of the turbineand for converting the waste-heat energy into energy for driving thesupercharging means and for driving the chilling means; and e. means forselectively controlling the portion of the waste-heat energy convertedto energy for driving the supercharging means and for driving thechilling means for providing selective control over the amount of energyavailable to superchill the inlet gas thereby providing for selectivecontrol of the performance of the gas turbine.